A workshop on primary immunodeficiency diseases was held in Geneva in 1977 under the auspices of the World Health Organization. A report of this conference was published under WHO auspices and was extremely well received by the medical and research communities. Subsequent to this, there was another meeting on immunodeficiency which was sponsored by INSERM in France in July, 1980. The proceedings of this meeting has been published by Elsevier Press under the title of "Primary Immunodeficiencies." The current conference has been planned because of the accumulation of information on immunodeficiency diseases. The workshop will cover the function of macrophage in the immune process, identification and function of T cells and T cell subsets, ontogeny of B lymphocytes, the role of enzyme deficiency, with particular emphasis on the purine degradation pathway. Also, methods in transplantation, thymic replacement will also be discussed and the use of long-term lymphoid cell lines to study diseased states will be examined. For this workshop, 40 investigators from Europe, Australia, the United States and Asia will be invited to attend.